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Astrometric plates obtained at the primary focus of large aperture reflectorsComa, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.
Document ID
19850016711
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Markos, A.
(Karlova Univ. Prague, Czechoslovakia)
Date Acquired
August 12, 2013
Publication Date
November 15, 1984
Publication Information
Publication: JPL Cometary Astrometry
Subject Category
Astronomy
Accession Number
85N25022
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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